Geoinformatics 2004 Proc. 12th Int. Conf. on Geoinformatics − Geospatial Information Research: Bridging the Pacific and Atlantic University of Gävle, Sweden, 7-9 June 2004 187 REPRESENTATION OF MOVING OBJECTS ALONG A ROAD NETWORK Nico Van de Weghe 1 , Anthony G. Cohn 2 , Peter Bogaert 1 and Philippe De Maeyer 1 1 Ghent University - Department of Geography, B-9000 Gent (Belgium), {Nico.VandeWeghe, Peter.Bogaert, Philippe.DeMaeyer}@UGent.be, Tel: +32 (0)9 264 46 96, Fax: +32 (0)9 264 49 85 2 University of Leeds, School of Computing, Leeds LS2 9JT, United Kingdom, agc@comp.leeds.ac.uk Abstract Research has previously been conducted in the area of generating, indexing, modelling and querying network-based moving objects. However, little work has been done in building a calculus of relations between disconnected network-based mobile objects. In this paper an approach to qualitatively representing and reasoning about trajectories of pairs of objects moving along a road network is presented. We call this approach the “Qualitative Trajectory Calculus along a road Network” (QTCN). We start from the assumption that two objects are moving continuously towards each other or away from each other, and consider how to describe their joint trajectories. Since the distance between two objects is measured along the shortest path, specific attention will be given to changes in shortest path, and more specifically changes in direction of the velocity vector of an object with reference to the shortest path between two objects. A conceptual neighbourhood diagram is presented, that forms the basis for a representation of a conceptual animation. INTRODUCTION The most developed area of qualitative spatial representation concerns topological relationships, as exemplified by RCC (the Region Connection Calculus) (Randell et al., 1992) in which connection between spatial regions can be taken as a primitive notion to define many other spatial relations between them, including the eight base relations depicted in Figure 1. Assuming continuous motion, there are constraints, which can be imposed upon the way these base relations can change over time for any pair of spatial regions (Figure 1). The 4-intersection model gives a similar calculus (Egenhofer and Franzosa, 1991). EC (k, l) TPP (k, l ) TPPI (k, l ) NTPP (k, l ) NTTPI (k, l ) k l k k k l l l k l kl k l k l DC (k, l ) PO (k, l ) EQ (k, l ) Figure 1: The continuous transitions between the eight base relations of RCC.